The present invention relates to environmentally safe and low corrosive de-icers and a method of manufacturing same. According to the present invention, the de-icers comprise calcium chloride (CaCl2.2H2O) as an active ingredient, a stabilizer (such as those used in foods) and a vegetable calcium preparation as additives for anti-corrosion, and a soil property improver as an ice-melting accelerator. Therefore, the present invention provides the de-icers having much improved anti-corrosion properties for metals such as steel structures as compared to conventional low corrosive de-icers, enabling to eliminate harmful damage to environment by using ingredients known as environmentally safe to plants and soils, and also enabling to mix the ingredients of the compositions more uniformly during manufacturing process, while still retaining the essential property of fast dissolution as a de-icer by introducing a system to optimize conditions such as temperature, mixing ratio, mixing speed and duration of mixing.
Calcium chloride and salt (rock salt) are most commonly used as de-icers during the winter season. They have advantages in that they are inexpensive, exhibit superior initial ice-melt activity due to the heat generated during their dissolution, and also prevent them from being refrozen by lowering their freezing point, however, they also have a disadvantage that they can corrode metal parts of a bridge due to their highly corrosive nature as described in the following table 1.
Therefore, studies have been focused on developing organic salts of non-chlorine type de-icers but they do not appear to be applicable because they are rather expensive and also not sufficient with respect to the initial ice-melt activity. Korea Pat. No. 99-219190 discloses a low corrosive ice-melting composition comprising salt or calcium chloride as an active ingredient and many similar U.S. patent applications have been filed since 1994.
The following table 2 shows registered patents which employ the addition of an anticorrosive agent or an ice-melt accelerator to the conventional de-icers which contain salt or calcium chloride as an active ingredient. The anticorrosive agents used in the patents of the following table 2 are shown to inhibit the corrosion of metals by protecting their surface via adsorption while ice-melt accelerator are used along with de-icers to expedite the deicing speed by activating the interface of ice by using a heat generating compound or a de-icer. However, the conventional low corrosive de-icers contain excessive amount of additives to prevent corrosion and thus there exists a great danger that they may damage the environment and it is noted that there is also a patent that uses phosphate type salt which is prohibited to use in several states of U.S.
U.S. Pat. Nos. 5,482,639 and 5,683,619 disclose additives used in manufacturing low corrosive de-icers and the process of manufacturing the same. Most of the patents shown in the following table 2 are concerned with the additives which are used to reduce the corrosiveness of the conventional de-icers. However, it should be noted that the process of manufacturing a low corrosive de-icer plays a crucial role in retaining and maintaining the essential properties of a de-icer required during the addition and mixing of additives.
The de-icers shown in the above table 2 can be divided into two different groups of inventions; inventions which include the use of all the compounds that prevent corrosion and inventions which reduce the corrosion by using the intrinsic properties of selected compounds. However, compounds that prevent corrosion have been described in numerous reports and many of them are compounds that are prohibited to be used in most states of U.S. because of their harmfulness to the environment. Therefore, it is in urgent need to develop a de-icer and its manufacturing method which has an excellent anti-corrosion activity as well as an excellent ice-melt activity while not being harmful to plants or soils.
To resolve the above-mentioned problems, the inventors of the present invention conducted their studies on the development of de-icers which are much less corrosive to metals than the conventional ones by using compounds of harmless food additives; are colored for easier identification of the amount of sprayed de-icers as well as their presence, and have fast rate of dissolution during ice-melt. For these purposes, anticorrosive compounds selected from the group consisting of known harmless food additives, calcium preparations for fruit trees, soil property improvers, and calcareous fertilizers were introduced to reduce corrosive properties of de-icers; colors were introduced by using the color change indicators based on the acid/base property as compared to the conventional white de-icers. Further, considering the importance of the mixing conditions of additives and color formers, which can result in change in shapes of de-icers and affect the melting activity, the inventors of the present invention set up mixing conditions optimal for manufacturing de-icers and finally completed the present invention.
Therefore, the object of the present invention is to provide excellent de-icers which are environment-friendly as well as low corrosive thus enabling to secure the safety of steel structures.